Organic vapor respirators, hereafter called respirators, are used as a means of protecting individuals from the inhalation of organic vapors. The protection provided by the respirator is derived from the use of an adsorbent, generally activated carbon, which adsorbs the organic vapor. Normally, the adsorbent is held in a cartridge or canister which can be replaced when the adsorbent loses its effectiveness, i.e., when the individual is no longer protected by the respirator because the adsorbent has lost its ability to remove toxic amounts of the organic vapor from the air. However, the duration of effective protection varies and depends upon a number of parameters such as the quantity of adsorbent, the particular organic vapor, the concentration of the organic vapor in the air, the humidity, the temperature, the nature and condition of the adsorbent, etc.
Because of this variability in the length of cartridge effectiveness, a number of attempts have been made to assess these parameters and derive a means of predicting the duration of cartridge protection in particular environments.
Current methods of determining respirator cartridge life are complicated, slow and expensive; therefore many organic vapors are completely untested, or untested in a variety of environments. Conventional respirator testing is performed with an apparatus similar to that described by Walter E. Ruch et al.: Respirator Cartridge Efficiency Studies I. Experimental Design, Am. Ind. Hyg. Assoc. J. 33: 105, 107 (1972) and Gary O. Nelson et al.: Respirator Cartridge Efficiency Studies II. Preparation of Test Atmospheres, Am. Ind. Hyg. Assoc. J. 33: 110, 111, 112 (1972).
In the conventional method a dynamic apparatus, an apparatus which continually produces a known concentration of a humidity-adjusted air/organic vapor mix, generates a flow of contaminant organic vapor mixed with air. The air/organic vapor mix is passed through an upstream analyzer, i.e., an analyzer positioned to measure the contaminant concentration before it reaches the respirator cartridge, and a second analyzer downstream which measures the contaminant level after the air/organic vapor mix has passed through the respirator cartridge being tested. The respirator cartridge life, also known as the breakthrough time, is that time duration measured from the time of the initial exposure of the respirator cartridge to the organic vapor contaminant to the time at which the contaminant is no longer completely retained by the cartridge. When the organic vapor traverses the respirator cartridge it is detected by the downstream analyzer.